Processing, May 2018

Filtration Separation Process coolant filtration Mov i n g b e yond nyone who has ever had to clean a clogged heat exchanger fully understands the need to keep coolant contamination out of the process stream Making that happen A almost always depends on implementing a series of increasingly e ective ltration technologies between the coolant source and the nal application The basics A system sourcing cooling water from a river or the ocean for example will typically include intake bars to block oating debris a 3 8 inch to 3 4 inch screen a 1 32 inch strainer and a lter to trap particles larger than 25 microns Once it is in the process loop the water will probably be ltered again before it is recycled to remove scale and other contaminants originating in the piping and process equipment e engineers designing that ltration system have to consider a number of factors including but not limited to e water and or uid source e source volume and nature of likely contaminants Heat exchanger materials and technology Process pressures and temperatures Acceptable downtime if any for lter maintenance Capital and long term operating cost It is obvious that no one size ts all prepackaged solution is likely to be successful in such an environment The reality is that engineering a filtration strategy for process cooling uids can be every bit as challenging as developing a ltration solution for the process products themselves To begin with the water source and the contaminants it is likely to contain will in uence the type of media used in a strainer or lter Sand for example is easily trapped in a porous lter medium because it does not change size or shape On the other hand an organic contaminant like pond scum is an entirely di erent challenge that is best handled with mechanically cleanable media Rain is a complicating factor that contaminates surface water with a broad range of organic and inorganic contaminants Each of these presents a different challenge that has to be quanti ed and accommodated based on speci c local conditions Once the water is in the system it is probably going to be chemically treated to reduce corrosion in piping and heat exchangers Depending on the application it may be ltered again to remove particulates under 25 microns that made it through the primary ltration system In any case clean treated process water represents a signi cant investment that is why it almost certainly will be recycled through a secondary heat exchanger and recirculated through the process system To protect that investment and the equipment it interacts with the water should be ltered once again to remove any particulates it has picked up from piping heat exchangers or other process equipment Except for the initial removal of coarse contaminants the water will be processed with a combination of strainers and lters Both perform essentially the same function but lters remove much smaller particles than strainers If you can see it you can strain it otherwise use a filter is a common rule of thumb In practice it means that particles in the range of 0003 inch to 0004 inch 007 to 01mm 75 to 100 microns 200 to 150 mesh can be removed e ectively with a strainer and anything smaller including particles down to a few microns will require a lter Both strainers and filters require periodic cleaning to remove the buildup of particles trapped in the media In a basic system using a simple basket type strainer or a bag type lter maintenance can be as simple as shutting off the flow manually removing the basket and dumping the trapped debris Obviously that means the process is either shut down during strainer and or lter maintenance or it is unprotected while the lter or strainer is bypassed Neither situation is optimal 42 Processing MAY 2018 t h e b a s i c s Optimize system performance and long term operating costs by selecting the right lter the rst time By Vincent Amarosa P E Eaton Corporation Image courtesy of Eaton Corporation via Getty Images

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